Oxidative sweetening with alkaline material and imidazole derivative



7 2,978,405 I OXIDATIVE SWEETENINGWITH ALKALINE MA- TERIAL AND IMIDAZOLEDERIVATIVE Rolland G. Bowers, Perrysburg, Ohio, assignor'to Sun" OilCompany, Philadelphia, Pa., a corporation of New Jersey c No Drawing.Filed June 18, 1959, ser. No. 821,098

7 Claims. (Cl. 208-206) V V This invention relates to sweetening sourhydrocarbon vdistillates, and more particularly to a manner of providingincreased sweetening rate.

According to the present invention, a novel manner I is provided ofobtaining m ore rapid sweeting. This result is obtained by carrying outthe sweetening operation in the presence of an imidazole having in themoleculea radical containing at least'l2 carbon atoms;

The imidazoles which can be used include imidazolines andbenzimidazoles. They can be prepared by known reactions of carboxylicacids with polyamines. For example,'reaction of carboxylic acid withphenylene diamine and its derivatives gives substituted benzimidazoleswhere the substituent in the two position is the radical which wasinitially attached to the carboxylgroup in the acid. Reaction ofcarboxylic acid with acyclicpolyamines, e.g. ethylene diamine and itsderivatives, gives substiituted imidazolines. Again, the substituent inthe 2-position is the radical initially attached to the carboxyl in theacid, and the carbon atom of the carboxyl becomes a member of theimidazole ring, being attached by a double bond to one nitrogen atom ofthe'original p'olyamine, and by a single bond to. another nitrogen atomof the polyamine. Various derivatives of ethylene diamine, e.g.diethylene triamine,'N-hydroxyethyl ethylene diamine, etc., giveimidazolines variously substituted in the l-position, e.g. byaminoethyl. and hydroxyethyl radicals respectively in the case of thesederivatives.

Quaternary salts of the imidazoles are beneficially employed accordingto the invention. 'These may be obtained by suitable known methods, e.g.the. reaction of the free base 'with a halohydrocarbon,e.g.-benzyljchloride, hexadecyl chloride, methyl bromide, etc.,jor withasulfated hydrocarbon, e.g. ethyl sulfate, etc. known methods can beemployed.

Preferred imidazoles for use according to the invention are those havingthe formula:

. N R-C -X where R is a hydrocarbon radicalcontaining 12 to carbonatoms,-R is selected from the group consisting of .hydrogen, hydrocarbonradicals, hydroxyaliphatic radicals, acylhydroxyaliphaticradicals(obtainable byesterifi .cation of the hydroxyaliphatic:radicals withcarboxylic acids), amino-aliphatic"radicals, and acylazninoaliphaticradicals (obtainable by amidification ofthe aminoaliphat- .ic radicalswith carboxylic. acids), R having molecular weight not greater than 300,and Xis selected from the group consisting of alkylene and phenyleneradicals.

More preferred imidazoles for use according to the invention are thequaternary salts having the formula:

.N. g l

results. r 7 V The. known phenylene diamine compounds for use in vinhibitor sweetening are generally suitable for use acwhere R, R, and Xare as defined above, and where R" is selected from the group,consisting of hydrocarbon radicals and halohydrocarbon,radicals having1 to 30 carbon atoms, and A is an anion selected from the groupconsisting ofhalide and sulfate ion.

Examples of suitable imidazoles are the followingzrZ- heptadecenylimidazoline; 'Z-abietyl-l-ethyl-3,4-dimethyl imidazoline; Z-naphthenyl1' hydroxyethyl imidazoline and the acetyl derivatives thereof;Z-heptadecadienyl-laminoethyl imidazoline'and the lauroyl derivativethereof;*2-undecyl benzimidazole; quaternary salts of the above withbenzyl chloride, hexadecyl chloride, methyl bromide, ethyl sulfate; etc.

" The: amo'untrof imidazole in the sweetening mixture according to;theinvention is preferably in the range from 0.001 to 1.0 weight percentbased on hydrocarbon charge stock. Smaller amounts can be used in somecases, though generally with decreased effectiveness. Greater amountscan be used, and quite effectively, but are usually avoided becauseunnecessary for satisfactory cording to one embodiment of the invention.The most commonly used compound is N,N-di-secondary-butyl-pphenylenediamine. compounds include.N,N-di-isopropyl p phenylene diamine,N,N'-di-secondary-amyl-p-phenylene diamine, N-isopropyl-NT-secondary-butyl-p-phenylene diamine,N-isopropyl-N-secondary-amyl-p-phenylene diamine, N sec-"ondary-butyl-N'-secondary-amyl p phenylene diamine,

etc. The amount of phenylene diamine compound employed is generallywithin the approximate range from 0.0001 to 1.0 weight percent based onhydrocarbons,

more preferably, 0.001 to 0.1 weight percent. However, any amount knownto be suitable for inhibitor sweetening can be used.

The alkaline material in the sweetening mixture is anaqueous solution ofalkali, e.g. alkali metal orammonium hydroxide or carbonate. Typically,the alkaline material is a 5 to 20 weight percent solution though otherconcentrations can be used. The amount of alkaline material ispreferably in the range from 0.01 to 5 weight percent though any amountknown to be suitable for 7 Other. I

use in oxidative' sweetening can be used.

The temperature conditions of the sweetening operation according to theinvention can be those which -are mp h entiqna .sw tsaia ,srsratieas- 1larly duringthe operation, or.it can be provided, periodipally or.continuously during the operation. ln some icasesat least, thepresenceof theirnidazole accordingfto the invention reduces the extent of theagitation nee toLprovide satisfactory sweetening rate. V A 1Molecularoxygen is requiredfqr the sweeteningjpp ration. Frequently,petroleum distillates normally contain Preferably, relativelylowtemperatures, e.g. in the range from 50F. -to F., are employed inorder to-favor the dispersion of the ,alkaline -rnaterial in the,hydrocarbons. However, higher temperatures can be employed if desired.

Agitation of the sweetening mixture promotes the conversion ofmercaptans. Agitation can be provided. only at the beginning of the.sweetening operation, orflirregusufficient dissolved oxygen to obtainsubstantial sweeteni Additional oxygen canbe'sup plied, regularly. r grly,,jit needed. it

a The Process ac t e. inventions.wa kabl generally to those mercaptan-containing petroleum fracq Such a ql nezinarhtha; kcroseneiianduelgdi fra t ons. wh hare n wn iwaa e e rw th s u9u .al a .-...A. typicl-ch is a 62API, 400 endpoint, catalytically crackdiand b suscep b e. op

Other suitable phenylene diamine 2,978,405. r I l caustic-pretreatedgasoline containing about 0.01 weight percent rnercaptan sulfur, but theapplicability of the invention to other known charge stocks forinhibitor sweetening and other oxidative sweetening processes with 4 theimidazolinium chloride, the used caustic, and the phenylene diamineagent.

In the absence of the phenylene diamine, used caustic containingcresylates is apparently relatively ineffective.

alkali will be readily apparent. 6 A mercaptan sulfur content of 0.0043wt. percent at 64 The following examples illustrate the invention: hoursis obtained with imidazolinium chloride present, as

Example 1 compared with 0.0036% for fresh caustic. A mixture of equalparts of sour gasoline and furnace Example 3 oil, the mixture containing0.0059 wt. percent of me r- 10 The procedure of example 2 is repeated,using fresh captan sulfur, is contacted at room temperature with 20 Baumcaustic, but omitting the phenylene diamine 2.5 volume percent of 20Baum caustic soda based on agent. In one experiment, the imidazoliniumchloride is the hydrocarbon mixture, with pounds of N,N-di-secpresent,in the other it is absent. The following table ondary bntyl phenylenediamine per 1000 barrels of shows the results: hydrocarbon mixture, andwith pounds of an imidazolinium chloride composition per 1000 barrels ofhydro- Mercaptan Sulfur Content carbon mixture.

The imidazolinium chloride used is a mixture of two TlmemHomImidazolinium Imidazollnium compounds having the following formula: Egg?N-CEg 22 0. 0041 0. 0049 64 0. 0030 0. 0049 N-CH:

HocHzcfii CHzCHtCH2CHzC1 These results show that the imidazoliniumchloride acwhere R is whemadecenfl in one f the compounds and 25celerates oxidative sweetening with caustic in the absencen-heptadecadienyl in the other. The composition emof a PhenYleQe fhammemhlbltorployed as additive here contains 60% of the imidazo- Generally511ml? resultsfo these obtamed f linium chlorides and 40% isopropanol,and has specific eedmg m are obtalned e other 1m1dazeles, gravity at 60F f 0960 and point less than phenylene diamine agents and alkalinematerials such as. minus F. those disclosed previously.

The hydrocarbon mixture, caustic soda, diamine and The invemlon claimeeis: quaternary imidazole salt are shaken together for one Process Predue 1g the mereaptan content of hour, then allowed to stand for 5hours. Sufficient disdreearbons whleh eompflses COMPCfiUg hydrocarbonssolved oxygen is present to oxidize mercaptans and retamms mereaptanswlth tfeaimg materials e 'f duce the mercaptan sulfur content to 0.0045wt. percent essentlany oeaqueous e f oxygen and an lmldazole at 5 hoursafter first contact. At 6 hours after first conhavmg a radlcal eontemmgat least 12 carbon atomstact, 100 cc. of air per 400 cc. of hydrocarbonmixture Process f reduemg mereaptfm content of are injected, and thesweetening mixture shaken for 15 drocafbpns whleh eompflses eentaetmghydroeafbons minutes, then allowed to stand for the rest of the experi-40 contalPmg mercaptans treatmg materials eollslsting ment. At 64 hoursafter first contact, the mercaptan essentlauy of aqueousalkehgoxygeniaphenylene dlamme sulfur content is 00017 wt percentsweetening agent and an imidazole having a radical con- To determine theeffect of the quaternary. imidazole tammg atleast 12 eafbon salt, anidentical experiment is performed in which the aeeofdmg to 2 wherein theaqueous salt is omitted. The following table shows the result: .alkahPresent eeneentratlon of about Volume percent based on hydrocarbons. M4. Process according to claim 2 wherein the imidazole is a quaternaryimidazolinium salt. Time in Hours Imidazommm Imidazonnmm 5. Processaccording to claim 4 wherein the imidazole Chloride Chloride has theformula Present Absent 60 N g R/ RII These results show the increase insweetening rate obmined with the imidazolinium Chloride where R is ahydrocarbon radical containing 12 to 30 carbon atoms, R is selected fromthe group consisting Example 2 ofdhayldrogen, hydrocarbon radicals,hydroxyaliphatic The rocedure of Exam le 1 is re eated,-with imidam {cacylhydroeyallghamradicals ammoa-hphauc zoliniur ri chloride present,omitting however the injecigs f i l fiigi gggis g gg ggg gi z i izg gg;tion of additional air and the additional-shakin ter 6 hours. In oneexperiment, fresh caustic soda is u s ed, as g iggig g gz j f gfigg g gi l gggi in Example 1, and in another experiment, caustic soda from themu n f 1 is used which has previously been employed to refine p co mg 0aryene an a yene 1' cracked gasoline and contains cresylates extractedfrom $52 gig 3 2 2 1332 g from the group consistfig zigi J :E: zoperanon' The fonowmg 6. Process according to claim wherein R ishydroxyethyl, R" is a chlorobutyl radical, and A is chloride.

7. Process according to claim 5 wherein R is hydroxy- Time in HoursFresh Used ethyl, R" is benzyl, and A is chloride.

Caustic Caustic 7O 22 M040 0,0033 References Cited in the file of thispatent m 0.0033 0. 0024 UNITED STATES PATENTS 2,616,831 Rosenwald Nov,4, 1952 These. results show particularly good cooperation bewveen2,674,566 Oosterhout eta1. Aug. 6, 1954

1. PROCESS FOR REDUCING THE MERCAPTAN CONTENT OF HYDROCARBONS WHICHCOMPRISES CONTACTING HYDROCARBONS CONTAINING MERCAPTANS WITH TREATINGMATERIALS CONSISTING ESSENTIALLY OF AQUEOUS ALKALI, OXYGEN AND ANIMIDAZOLE HAVING A RADICAL CONTAINING AT LEAST 12 CARBON ATOMS.